DRAG REDUCTION ON 20 MM AIRCRAFT CANNON PROJECTILES UTILIZING OPTIMAL FOREBODY SHAPING

UTILIZING AN ITERATIVE-DIRECT DESIGN PROCEDURE TO OBTAIN MINIMUM DRAG AXISYMMETRIC BODIES, DEVELOPED BY THE PRINCIPAL INVESTIGATOR FOR EGLIN AFB, THE PROPOSED RESEARCH SEEKS TO CHARACTERIZE OPTIMAL FOREBODY SHAPES OF 20 MM AIRCRAFT CANNON PROJECTILES. THE WORK SHALL EXTEND THE BOUNDARIES OF CLASSICAL HYPERSONIC INVISCID FLOW OPTIMUM BODY THEORY BY ACCOUNTING FULLY FOR THE EFFECT OF THE VISCOUS FLOW ON A SPINNING AXISYMMETRIC SHAPE. BOTH FRICTIONAL DRAG AND FORM DRAG (DUE TO VISCOUS - INVICID INTERACTIONS) MODIFICANTIONS TO CLASSICAL RESULTS SHALL BE PRESENTED AS A FUNCTION OF MACH AND REYNOLDS NUMBER. THE OFF-DESIGN PERFORMANCE OF EACH OPTIMUM SHAPE SHALL ALSO BE ASSESSED IN ORDER TO OBTAIN BODIES WHICH PROVIDE NET OPTIMUM PERFORMANCE OVER THE RANGE OF MACH AND REYNOLDS NUMBERS ENCOUNTERED: 1) ALONG A GIVEN TRAJECTORY OR, 2) ON VARIOUS AIRCRAFT MISSIONS. THE EFFECT OF UNSTEADY FLIGHT, DUE TO THE DRAG-INDUCED DECELERATION, ON THE FLOWFIELD AND RESULTANT CD SHALL ALSO BE QUANTIFIED. FINALLY, THE PHASE II WORK PLAN SHALL BE PREPARED INCLUDING A COMPUTATIONAL EFFORT TO DEVELOP A COMPREHENSIVE LIBRARY OF OPTIMAL SHAPES, ANALYSIS OF STEADY AND DYNAMIC ANGLE-OF-ATTACK THREE-DIMENSIONALITY, AND THE FORMULATION OF AN EXTENSIVE FIELD TEST VALIDATION OF THE PHASE I RESULTS.